code: def train_fn(config):
      this_node_ip = ray.util.get_node_ip_address()
      if config["head_node_ip"] == this_node_ip:
          # On the head node, run for 30 minutes
          for i in range(30):
              train.report({"metric": i})
              time.sleep(60)
      else:
          # On worker nodes, run for 3 minutes
          for i in range(3):
              train.report({"metric": i})
              time.sleep(60)
  
file_path: ray/release/cluster_tests/workloads/tune_scale_up_down.py
imports: from collections import Counter
  import time
  import ray
  from ray import train, tune
label_desc: Use image node_id 1 for calling a global function with example usage: train_fn(config) without return types